Stabilization of halogenated hydrocarbons



United States Patent STABILIZATION OF HALOGENATED HYDROCARBONS William R. Dial, Akron, Ohio, assignor to Columbia- Southern Chemical Corporation, Allegheny County, Pa., a corporation of Delaware No Drawing. Application June 15, 1953, Serial No. 361,845

Claims. (Cl. 260-6525) This invention relates to the stabilization of halogenated aliphatic hydrocarbons and it particularly concerns the stabilization of chlorinated aliphatic hydrocarbons. It further relates to stabilized compositions containing halogenated aliphatic hydrocarbons, notably chlorinated aliphatic hydrocarbons such as perchloroethylene.

It is known that chlorinated hydrocarbons such as perchlorocthylene have a tendency to decompose during use, storage, and shipment. This tendency is known to be more pronounced when the chlorinated hydrocarbon is in contact with metallic surfaces such as iron or copper. Such decomposition renders these compounds objectionable when they are employed for certain commercial operations.

One of the important commercial uses of perchloroethylene is as a solvent, for example, in dry cleaning of wearing apparel, rugs, or other fabric materials. It is an excellent solvent for oils and greases. However, when it decomposes, the products of decomposition interfere to such an extent as to materially injure its beneficial effect. When employed in metal structures, the problem of metal corrosion caused by the decomposition of the perchloroethylene is quite serious.

Moreover, these chlorinated hydrocarbons, and notably perchloroethylene have shown poor light stability. That is, under the effect of light, notaly ultraviolet light or light of equivalent wave length, such as light from a fluorescent light, a change in the pH of the compound is observed. This change in the compound is often undesirable.

Various chemicals have heretofore been proposed for use as stabilizers for halogenated aliphatic hydrocarbons. Among those which have been suggested are benzaldehyde, cyclohexane, toluene, benzyl chloride, amylene hexylresorcinol, butyl mercaptan, ethyl acetate, guanidine, pyridine, and others. For certain purposes, these compounds are unsatisfactory in that they are ineifective stabilizers for perchloroethylene, or their odor or color is objectionable.

According to this invention it has been discovered that chlorinated hydrocarbons, notably perchloroethylene, are stabilized satisfactorily when a small, stabilizing quantity of an alkylaminoalkylcyanide is added thereto. The resuiting stabilized compositions possess acceptable odor 2,781,406 Patented Feb. 12, 1957 The contemplated stabilizers have the following chemical structure:

wherein R is hydrogen or an alkyl group containing 1 to 3 carbon atoms, R is an alkyl group containing '1 to 3 carbon atoms and R is an alkylene group containing 1 or 2 carbon atoms such as CH2- or -CH2CH2-.

Typical of the alkylaminoalkylcyanides which may be utilized to stabilize the chlorinated hydrocarbons are monoalkylaminoalkylcyanidcs such as beta-N-isopropyl arn'inoethylcyanide, beta N methylaminoethylcyanide, beta-N-ethylaminoethylcyanide, beta-N-methylaminomethylcyanide, N-ethylaminomethylcyanide and N-isopropylaminomethylcyanide. Dialkylaminoalkylcyanides include N,N dimethylaminornethylcyanide, N,N diethylarninomethylcyanide, N,N di-isopropylaminomethylcyanide, beta-N,N-dimethylaminoethylcyanide, beta-N,N-diethylaminoethylcyanide, and beta N,N di isopropylaminoethylcyanide.

The amount of the alkylaminoalkylcyanide which is required to stabilize perchloroethylene, or like chlorinated aliphatic hydrocarbon, is exceedingly small. About 0.005 to 0.01 percent of the alkylaminoalkylcyanide, by weight of the composition, is desirable for optimum results. Somewhat smaller quantities of the alkylaminoalkylcyanide in the perchloroethylene compositions also provide a stabilizing effect. The concentration of the alkylaminoalkylcyanide may be as high as about 1 to 2 percent, or higher, if economically feasible. Perchloroethylene stabilized with the alkylaminoalkylcyanide has been observed to remain stable over considerable periods of time even after repeated distillations in a simple still.

The stabilizing effect of the alkylaminoalkylcyanide on perchloroethylene has been established, according to the invention, by means of a test conducted over a 72-hour period. The test is performed by refluxing perchloroethylene in a flask in the presence of water, strips of copper, and the stabilizer. One hundred milliliters of perchloroethylene is placed in a 300-milliliter flask and 0.2 milliliter of water is added. The flask is attached to a small Soxhlet extractor and a bulb type Allihn condenser is attached to the extractor. One weighed copper strip is placedin each of the flask, extractor, and condenser. The copper strip which is placed in the condenser is placed so that the perchloroethylene condenses on the strip. The condenser is connected to a water scrubber to absorb any HCl evolved during the test. The perchl-oroethylene is heated to boiling point, the heating being carried out so that the extractor empties at 8 to 10-minute intervals. A IOO-Watt incandescent bulb is placed one inch from the vapor line of the extractor to furnish energy for photochemical oxidation.

After the test is completed, part of the water in the scrubber is poured through the condenser a-nd extractor and finally into the flask. The water and perchloroethylone are poured into a beaker, phenolpht-halein is added, and the water layer is titrated with 0.01 N NaOH. The copper strips are weighed to determine their weight loss during the test.

The light stability of perchloroethylene was determined by the following procedure. A fluorescent fixture with a 13 by 50-inch white reflector and two 40-watt, 47-inch, cool-white bulbs spaced on S-inch centers, such that there was a 36-inch space between the bulbs, was mounted in a cradle upside down. One hundred-millimeter samples of the perchloroethylene composition to be tested for light stability were placed in 250-milliliter, glass-stoppered,

bons.

squatty-type, clearglass bottles. These sample-containing bottles were placed between the bulbs in the 3Vz-inch space and exposed for 24 hours to the light from the two bulbs. "-No bottle" was' placed within fi' inches of either 'end of the bulb. The pH of the samples at the conclusion of the exposure was determined, as was the prior to such exposure. A difference in pH of over 1 indicated poor light stability.

The following table presents the data observed when the above-described tests were made.

4 alkyl group of 1 to 3 carbon atomsand R is an alkylene group selected from the group consisting of -CH2 and -CH2-CH2.

3. The method of claim 2 wherein the chlorinated hydrocarbon is perchloroe thylene.

4. The method of stabilizing chlorinated aliphatic hydrocarbons containing up to?"carbon'atoms which comprises adding there'toa small stabilizing quantity of beta- N,N-dimethylaminoethylcyanide. I 10 "5.A composition"comprising-a*halogenated aliphatic pH Copper weight loss, milligrams w 'i hsa... a Stabilizer percent 7 Acidity 'stabillze'r -Original Photoxi- Flask Extrate- Gondation tion denser None 6. 8 2. 500 9. (3 l7. 6 409. i] beta-N-isopropylamino-ethylcyanide. 9. 1 9. 1 v 0.0 2.8 1.3 i 1. 7 beta-N,N-dirnethylamino-e'thylcyanid 8. 6 8. 0. t) I. 3 2. 9 3.0 N,N-diethylamino-niethylcysnide. 8. 5 1. 3 3. 3 9. 1 7. 4

1 A'cidity'in milliliters of OJOI-N 'NQOH per GU-milliliters of (2201.. These tests 'establi'sh the improvement in stability of 'pe'rchloroe'thylene providedbythe addition of the alkylaminoalkylcyanidethereto such as described above. Other halogenated aliphatic hydrocarbons 'containing'up toand including 3" carbon a'tomsfa'nd'notably 'thechlorinated hydrocarbons, such as carbon tetrachloride, chloroform; and trichloroethylene; may be stabilized in accordance with this invention by adding 'a'stabilizing quantity-of the 'alkylaminoalkylcyanide thereto. I

Alkylaminoalkylcyanides may beemployed'alone or they'may be used in conjunction Withotherstabilizers to provide stabilized compositions of halogenated hydrocar- When it is used in cooperation with other stabilizers, it is often'possible to'employ much lower concen trations of the alkylaminoalkylcyanide than'wh'en 'it' is used alone, e. g. concentrations of the order of from 0.0025 percent to 0.005 percent by' weight'are adequate. Although the present invention has been described with reference to specific details of certain embodimentgit' is 'not intended that such details shall be regarded as limitations upon the scope of the invention, except insofar as included in the accompanying claims.

I claim:

l. The method of stabilizing halogenated aliphatic'hydrocarbons containing up to 3 carbon atoms which co'mprises adding thereto a small stabilizing quantity of a compound having the structure wherein R is selected from the group consisting ot'hydrogen and an alkyl group of l to 3 carbon atoms,"R 'is'an alkyl group of lto 3 carbon atoms and R" is an alkylene group selected from the"group consisting of -'CH2 and CH2'-CH2. V

2. The method -'of stabilizingchlorinated aliphatic hydrocarbons containing up to 3 carbon 'atoms which 'co'r'nprises adding-thereto'asmall stabilizing quantity of a compound having'the structure wh'ereinR is selectedfrom the-group j consisting- 'of hydro gen and an alkyl group of l to 3 carbon atoms; R is an N-R"OEN R/ wherein R is selected from the group consisting of hydrogen and an alkyl group of 1 to 3 carbon atoms, R is an alkyl group of l to 3 carbon atoms and R" is an alkyiene group selected from the group consisting of CH2 and -CH2CH2.

7. A composition comprising perchloroethylene and a stabilizing quantity of a compound having the structure NR"CEn wherein R is selectedfrorri the group consisting of hydrogen and 'an'alkyl group'of 1 to' 3 carbon atoms, R"isan alkyl'group'of Ho 3 carbon atoms and R" is an alkylene group selected from the" group consistingof --CH2 and CH2CH2.

BJA composition comprising perchloroethylene and a stabilizing quantity of beta-N,N-dimethylaminoethylcyai nide.

9. A composition comprising a chlorinated aliphatic hydrocarbon containing 1 to 3 carbon atoms and a stabilizing quantity of beta-N-isopropylaminoethylcyanide.

10. A composition comprising perchloroethylene and a stabilizing quantity of beta-N-isopropylaminoethylcyanidc.

References Cited in the file ofthis patent UNITEDSTATES PATENTS 2,043j257 Mis'sba'ch June 9, 1936 

1. THE METHOD OF STABILIZING HALOGENATED ALIPHATIC HYDROCARBONS CONTAINING UP TO 3 CARBON ATOMS WHICH COMPRISES ADDING THERETO A SMALL STABILIZING QUANTITY OF A COMPOUND HAVING THE STRUCTURE 